We will continue to validate the one minute oxygen uptake during treadmill exercise at 1000 Kg in /min power requirement (P). We will place emphasis on the correlation between reduced values (less than 1.57 L/min for men between the ages of 30 and 60 years) and cardiac output measured at P equals 750 for 3 minutes of exercise. In addition, we plan to validate the CO2 rebreathing cardiac output which we have in use against an indicator dilution technique (green dye) and also initiate a prospective series of the effect of myocardial infarction (status at 3 months from hospitalization) on both one minute oxygen uptake at P equals 1000 and 3 minute cardiac output at P equals 750 (or a lesser stress if subject's condition so indicates).